This invention relates to a cell image processing system having a bus dedicated to image data. More particularly, the invention relates to a processing method and apparatus for extracting and memorizing cell images in which, even if a number of cells are present in a single imaged frame, a number of cell images can be processed efficiently in one frame cycle from information relating to the positions at which the cells reside.
The general architecture of an image processing apparatus having a bus dedicated to image data, as well as the operation of this apparatus, will now be described in simple terms.
FIG. 1 is a block diagram illustrating an example of an image processing apparatus having a bus dedicated to image data.
The apparatus includes a general-purpose microcomputer 12 which functions as the overall host processor of the system, a plurality of slave boards for processing an image in hardware fashion, and a master controller & processor 14 for controlling the operation and function of the slave boards. More specifically, each board is operated by having its operating mode, function and parameters set by the master controller & processor 14 via a slave board control bus 16. The boards are usually interconnected via a six-to-nine channel bus 18 dedicated to image data, with an eight-bit bus serving as one channel.
The data on the dedicated bus flows in the manner of a time series identical with that of a raster scan system in television, and one-sixtieth of a second is required to deliver all of the data in a single image frame. In other words, the bus dedicated to the image data employs horizontal and vertical synchronization as the timing base, and random accessing for a single image frame of data cannot be performed via the data bus 18. Because the dedicated bus uses vertical synchronization as a timing base, the processing performed by the boards connected thereto also has the vertical synchronization period (one-sixtieth of a second) as a single processing cycle. Accordingly, the setting of the operating mode, function and parameters of the slave boards by the master controller & processor is ordinarily carried out during the vertical blanking period. The master controller & processor not only controls the slave boards in accordance with an image processing request from the general-purpose microcomputer but also functions to compute such characterizing parameters as the cell edge trace, cell image area and perimeter of the cell images based on data obtained through processing performed by an image processor board 20. Futhermore, it is also possible for the master controller & processor to randomly access the contents of image memory boards 22, 24 via the slave board control bus, ascertain the position at which a cell appears, read the image data pertaining solely to this portion and compute other characterizing parameters.
The general operation of the common image processing apparatus set forth above will now be described taking as an example a case in which a still picture of cells flowing in a planar sheath is captured and the cells are classified in accordance with type by means of image processing.
A planar sheath flow refers to a flow having a thickness the same as that of the thickest particle among the particles of interest and a width which is a number of times greater than that of the widest particle, e.g., a width which can be 100 times greater or more, wherein the flow is such that the particles of interest in the flow will not overlap one another in the direction of the thickness. Examples of an apparatus in which a planar sheath flow is realized are disclosed in the specifications of Japanese Patent Publication No. 57-500995 and U.S. Pat. No. 4,338,024.
In order to acquire a still picture of cells in a planar sheath flow, strobe light or pulsed laser light having a short emission time is made to irradiate the flow in the thickness direction thereof, and an image is formed on the image pickup surface of a video camera (color camera) via an objective lens. The camera outputs analog signals resolved into the three colors R (red), G (green) and B (blue). These are fed into an image input board 28 which subjects them to an analog/digital (A/D) conversion. The resulting digital R, G and B data is stored in an image memory board 22 via a three-channel image data bus. At the same time, the data is inputted also to the image processor board 20, which executes preprocessing to determine whether a cell is in view and to detect the edge of the cell. Preprocessing entails extracting an average value of, e.g., G (green) and B (blue) data at each point (pixel) of an image and forming a histogram of the entire image frame in realtime. The data processed by the image processor board 20 is stored in the image memory board 24 via the dedicated bus 18. Though the method in which the two image memory boards 22, 24 are used is not particularly limited, in the present description the image memory board 22 is used to store original image data and the image memory board 24 is employed to store data which has been processed.
In one vertical retrace interval the master controller & processor 14 checks the histogram prepared in the image processor board 20 and determines whether a cell is present in a single image frame. If it is decided that no cell is present, then the program of the master controller & processor 14 returns to processing for the next new imaged frame. When a cell is found to exist, the program proceeds to the next image processing step. An example of the next image processing step would be processing for subtracting previously stored background data from the image data, preparing a histogram from the results obtained, digitizing the image data as preprocessing for the purpose of tracing the edge of a cell, and detecting the cell edge. The resulting edge detection data is stored in the image memory board via the bus dedicated to image data. By way of example, edge detection information might include eight-bit data made to correspond to each pixel of a single image frame, in which pixels that take on values other than 0 are regarded as cell edge points and the direction in which the next neighboring cell edge point is located is indicated by the particular value. When this processing is completed, the master controller and processor 14 refers to the edge detection information in the image memory board via the slave board control bus 16, and the edge of each and every cells traced by means of a microprogram. At the same time, computations for the area and perimeter of each cell, cumulative chromaticity information and shape parameters are performed. Each cell is then classified based on the characterizing parameters obtained.
In a system in which it is required to save (store) images of the cells observed, processing is necessary in which the position occupied by each cell in the frame is determined from the results of edge traces for each cell, only those regions of the original frame in which cells are present are extracted, and the regions are gathered together in accordance with each cell class and saved in the memory. The cell image data saved in accordance with each class is inputted to a display processor board 30 via the dedicated bus 18 and is displayed on a color monitor 32.
This completes the brief description of image processing performed by an image processing apparatus having a bus dedicated to image data.
A problem which the present invention attempts to solve concerns cell image extracting and memorizing processing in which processing for extracting and saving (storing) a number of captured cell images, as shown in FIG. 9, can be performed in a highly efficient manner.
Basically, the cell image extracting and memorizing processing mentioned above is performed in the following manner: From the results of the edge tracing of each cell, the master controller & processor ascertains the area in which each cell is present in one original imaged frame stored in the image memory. Ordinarily, this area is expressed by a perfect square, within which the data is transferred to another image memory so as to be saved. Though there are several ways in which the transfer can be performed, two typical examples of conventional methods will now be described.